The present invention relates to the batch fabrication of magnetic read/write transducers, and in particular to a stripe forming process which machines the transducer to a specific stripe height target.
Magnetic read/write transducers or sliders are typically produced by using thin film deposition techniques. In a typical process, an array of sliders are formed on a common substrate or wafer. As part of the formation of the sliders, electric lapping guides (ELGs) are also formed on the wafer, along with bond pads and electrical connections which allow for inspecting and testing the sliders. Using these electrical connections, the wafer is typically optically and electrically inspected, and is then sliced to produce bars, with one row of sliders in a side-by-side pattern on each bar. The bar is then lapped at the surface that will eventually face the recording medium. The ELGs are used to control the lapping process so that a desired magneto-resistive (MR) transducer height (also referred to as the stripe height) is achieved for every slider across the bar. After lapping, an air bearing pattern is formed on each slider on the bar and the bar is diced to produce individual sliders.
In order to establish adequate performance for high efficiency MR transducing heads, it is desired to achieve the specified stripe height with a very tight tolerance control. One common practice is to use ELGs in addition to on-line bending mechanisms to form a closed-loop controlled lapping process. Because the ELGs are fabricated with the actual MR transducers during the-same wafer processing, the ELGs are used to predict the stripe height for each slider and feed that information to the lapping device control system.
During the lapping process, material is removed from the surface of the bar. As material is removed from the surface of the bar, material is likewise removed from MR elements and the ELGs attached to the bar. The ELGs have a known resistence per unit of thickness so that as the surface of the bar is lapped, the resistence of the ELG changes. The ELGs are monitored during lapping to provide feedback indicating the amount of material being removed from the bar by the lapping device. In this manner, a stripe height profile can be created for the bar based on the material removal sensed by the ELGs.
In addition to ELGs used to predict the stripe height, the lapping device also commonly includes a fixture for holding the bar in place during lapping. The bar holding fixture may include a bending mechanism which can be controlled to manipulate the bar relative to the lapping mechanism, such as by bending or deforming the bar to move portions of the bar closer to or further away from the lapping mechanism. The stripe height variation across the bar can be minimized by using the predicted stripe height profile to control the bar fixture by adjusting the bending mechanism in response to the predicted stripe height profile.
An example of a prior art ELG can be found in U.S. Pat. No. 6,047,224, entitled, “MACHINING GUIDE FOR MAGNETIC RECORDING REPRODUCE HEADS.” An example of a device for lapping a bar of sliders can be found in U.S. Pat. No. 5,951,371, entitled, “MULTI-POINT BENDING OF BARS DURING FABRICATION OF MAGNETIC RECORDING HEADS.”
Data storage competition is continuously driven by fast increasing areal density, which in turn reduces the desired MR element stripe height to as small as 50 nanometers, with pressure building to even further reduce this height. The existing process control schemes using ELGs and a holder capable of bending the bar are often inadequate for achieving the desired stripe height for each slider on the bar within the tolerance required at such small dimensions.
Thus, there is a need in the art for a control scheme that enables direct head performance control during machining, which in turn provides improved slider yield capability.